This invention relates to a pitless well adapter and more particularly, it concerns a unique pitless adapter having a pressurized seal arrangement employing an anti-syphon check valve.
In early well systems employing a submersible type pump disposed within a well casing, a pit was formed around the well casing to a depth below the frost line. A delivery line was connected to the pump discharge line at the bottom of the pit where the casing was severed. From this point, the pumped fluid was directed underground to a storage tank or the like. This arrangement was unsatisfactory since employment of the pit permitted contamination of the well water by surface water. Further, due to the fact that the majority of these well systems were employed in rural areas in close proximity to residential waste treatment facilities, such as septic tank arrangements, the well water could be contaminated with human waste making it totally unfit for consumption.
As a result of these problems a pitless-type well was developed employing a two-part adapter connecting a delivery line to the pump through the well casing at a point below the frost line with the well casing extending above the surface. An example of this type of arrangement may be found in U.S. Pat. No. 2,689,611 to Martinson. As shown in this patent, a two-part adapter is employed including a hanger unit having a pipe nipple extending through an aperture formed in the well casing to which the delivery line is connected and a supported unit adapted to be supported by the hanger unit. The supported unit includes an L-shaped passage mating with the passage formed in the hanger unit. A drop pipe, disposed within the well casing, is connected to a submersible pump at one end and to the supported unit at the other end. A lift pipe is connected to the supported unit and serves as a means for positioning the pump and supported unit within the well casing. A gasket is placed in sealing engagement with the well casing around the pipe nipple portion of the hanger unit to prevent leakage of surface water and other contaminants into the well casing. However, in the event of gasket failure during service due to natural deterioration or due to improper installation, surface water would leak into the well casing and contaminate the well water.
As a result of this primary shortcoming, various sealing arrangements were developed for use between the well casing and the pitless adapter in an attempt to prevent contamination of the well water in the event of seal failure. An example of such an arrangement may be found in U.S. Pat. No. 3,306,358 to Williams. As disclosed in this patent, a two-part adapter, similar to the adapter disclosed by Martinson, is employed. However, inner and outer gaskets are placed between the hanger unit and well casing to define a pressure chamber. A passageway or aperture is formed in the hanger unit to permit communication of the pumped fluid with a pressure chamber defined by the inner and outer gaskets, the hanger unit and the well casing, thereby pressurizing the seal. See also Williams U.S. Pat. Nos. 3,403,730 and 3,561,796.
In the event of seal failure, while the fluid is being pumped, leakage would occur in an outward direction thereby preventing contamination of the pumped fluid by surface water. However, due to the fact that these systems generally employ a check valve disposed within the drop pipe (or associated with the submersible pump) which is subject to leakage as a result of wear or which may in fact have a designed-in leakage rate, water within the discharge line will flow downward, i.e., in a reverse direction, anytime that the pump shut off. Because the end of the delivery line connected to the residence is effectively closed, the receding water level in the delivery line draws a partial vacuum behind it. If this level recedes past the pitless adapter down the drop pipe, the seals in the Williams patent can be subjected internally to below atmospheric pressure. In the event of seal failure when this condition is present, ground water will enter the drop pipe through the passage which communicates with the now depressurized seal. This condition is potentially more dangerous than the leakage condition of the pitless adapter disclosed by the Martinson patent in that ground water directly enters the pumped fluid within the drop pipe and does not merely enter the well casing where it would be diluted with the water at the bottom of the well.